With climate change, a 9-foot water level rise isn't that far off.

Photos of various parts of New York City underwater due to Hurricane Sandy have abounded over the last 24 hours: subway stations submerged, water pouring into Ground Zero, and the FDR Drive merged with the nearby river. But these events might not be an aberration in the future. According to various climate change models, the ocean will rise to the highest levels brought on by Hurricane Sandy within the next couple hundred years. We could be looking at a preview of the New York City of 2200.

Granted, predictions of the sea level beyond the year 2100 have wide confidence intervals, and depend greatly on variables like greenhouse gas emissions and how quickly some of the larger ice sheets in Greenland and the Antarctic melt. But even allowing for the world to get its emissions under control within a reasonable time frame, New York will still see the water level rise by several feet, as it did during the hurricane, within the next century or two.

According to the National Oceanic and Atmospheric Administration's water level sensor at The Battery in Lower Manhattan, water levels were 9.23 feet above normal at their highest point, which happened at about 9:24pm last night. The water level rise was sustained above five feet for about ten and a half hours, from 2:24pm on October 29 until 1:18am on October 30.

A report published in Nature Climate Change in June projects that on our current emissions path, the sea level will rise 40 inches by 2100 and 7 inches per decade thereafter. At that rate, the sea level would hit the Hurricane Sandy proportions of 9 feet around the year 2200; the five foot rise will occur in just over a century. The same paper notes that even if global warming is held to 2 degrees Celsius, there's a 50 percent probability that the sea level will reach 9 feet by the year 2300—much further out in time.

Another paper published in September 2011 that examines the potential sea level rise to the year 2500 also shows that right around the turn of the 23rd century, the sea level will be up about 9 feet. (There will necessarily be some differences between the global sea level and the one local to New York, but most estimates show the effect in New York to be on par with or greater than the global one). The sea level would rise that high in this projection if greenhouse gas concentrations remained on the high side and these emissions were not stabilized until after 2100.

The sea level rise projections in meters (top), and the rate in meters per year (bottom), over time.

These projections depend on a number of factors, including the melting of ice sheets. Scientists expect the effects of the melting of ice masses like Greenland and Antarctica to take place over the next few centuries to millenia but cannot pinpoint the pace. It's highly unlikely any of the ice sheets will melt completely before the next few centuries are through. But if even 40 percent of Greenland's ice mass melted, that alone would raise the sea level by a maximum of 9 feet.

The eventual sea level rise won't be accompanied by Frankenstorm-level disaster scenarios, like water pouring in through an elevator shaft. And New York's system for pumping water out of the way of its infrastructure is not to be discounted; already, the subways only function by the grace of a powerful and elaborate water displacement outfit. Still, the hurricane provides a visual reminder of how susceptible coastal cities will be to getting enveloped by a rising ocean.

Casey Johnston
Casey Johnston is the former Culture Editor at Ars Technica, and now does the occasional freelance story. She graduated from Columbia University with a degree in Applied Physics. Twitter@caseyjohnston

Nitpick: the graph showing future rates of increase should be described as mm/year in the caption. If you only mention the rise in meters it can confuse the reader about the rate of rise.

Perhaps NYC should consider the approach of North Carolina: legislate that all future sea level predictions be based on purely historical data extrapolated into the future, instead of taking all that inconvenient science into account.

Perhaps NYC should consider the approach of North Carolina: legislate that all future sea level predictions be based on purely historical data extrapolated into the future, instead of taking all that inconvenient science into account.

Why not just go whole hog and legislate that planners must assume current sea level for all future planning?

"In the reconstructed analysis, there is no evidence of an acceleration in the long term rate of sea level rise, which remains at below 2mm/year. Furthermore an analysis of Southern Hemisphere sites suggests a slowing down in the rate. The sample sizes in both cases are small and give limited geographical coverage. Nevertheless, they give a similar coverage to the original Douglas study, which has generally been accepted as giving an accurate assessment of 20th Century rise. (For instance, the IPCC quote a figure of 1.7mm/year)."

2mm/year works out to 6.9 inches by 2100. Inches! Add another 7.8" for the next 100 years.

"In the reconstructed analysis, there is no evidence of an acceleration in the long term rate of sea level rise, which remains at below 2mm/year. Furthermore an analysis of Southern Hemisphere sites suggests a slowing down in the rate. The sample sizes in both cases are small and give limited geographical coverage. Nevertheless, they give a similar coverage to the original Douglas study, which has generally been accepted as giving an accurate assessment of 20th Century rise. (For instance, the IPCC quote a figure of 1.7mm/year)."

2mm/year works out to 6.9 inches by 2100. Inches! Add another 7.8" for the next 100 years.

Wattsupwiththat.com huh? Interesting source. Which university or climatology department does that site belong to?

Newsflash: Minimum first-floor elevation rise will make Hurricane Sandy's NYC trivial by the year 2200

The rise in water level caused by Sandy was only a problem because the last +100 years of NYC construction hadn't planned for it. I have a hunch that might change over the next 188 years. Maybe, just maybe, they'll even gradually raise the elevation at which they construct a building's foundation in order to accommodate for the gradual rise in waterline.

Makes the whole premise of this article somewhat disingenuous if you ask me.

Still, the hurricane provides a visual reminder of how susceptible coastal cities will be to getting enveloped by a rising ocean.

Humanity has been building settlements at sea level for about 6 or 7 thousand years now, and for some reason even after losing many of them to the waves, we have yet to learn that while we may like to pretend that we can build permanent structures, the ocean may have other ideas...

I don't find the topic "What will life be like when the sea is four meters higher?" as interesting as the direct contribution of climate change to the path and evolution of this particular storm, via the NAO, the Jet Stream and melting Arctic ice.

Newsflash: Minimum first-floor elevation rise will make Hurricane Sandy's NYC trivial by the year 2200

The rise in water level caused by Sandy was only a problem because the last +100 years of NYC construction hadn't planned for it. I have a hunch that might change over the next 188 years. Maybe, just maybe, they'll even gradually raise the elevation at which they construct a building's foundation in order to accommodate for the gradual rise in waterline.

Makes the whole premise of this article somewhat disingenuous if you ask me.

Making a taller building entrance won't keep the streets and sidewalks dry.

If anything, New York will be like New Orleans: above sea level when first built, but gradually surrounding it with levees to keep it dry and habitable.

Seems like a waste of time. I've been to Venice and, let me tell you, most of the streets are already flooded even when the weather is nice.

Yeah, I might be guilty of being a bit lazy in posting that. Venice has some real problems that needs to be addressed with more than just a gating system. I do wonder however how economical it might be to build such a system around cities where major damage caused by storms and associated flooding is sky high? Above a certain dollar amount it might make economic to install these to mitigate storm induced flooding.

OT: Homeless will still be homeless though regardless (you owe me a keyboard for that comment in another thread)

Still, the hurricane provides a visual reminder of how susceptible coastal cities will be to getting enveloped by a rising ocean.

Humanity has been building settlements at sea level for about 6 or 7 thousand years now, and for some reason even after losing many of them to the waves, we have yet to learn that while we may like to pretend that we can build permanent structures, the ocean may have other ideas...

True. Look at New Orleans, which sits in some places 10' below sea level. New Orleans is only occupied due to levies keeping the sea at bay. Also, Katrina wasn't the first time the levies broke and flooded the area, killing many. Florida is in similar shape with regard to coastal development. In some cases apartments and condos are built so close to shoreline that there are merely 10 to 20' between the foundation and the ocean. It seems people have learned nothing from thousands of years of coastal regions being ravaged by storms and tsunamis.

If science tells you something you don't like.... ignore it. It'll go away.But if we don't warn you...... OMG WE NEED TO HAVE US A LYNCHIN'!!!!

I've come to accept that some people just want to return to the Dark Ages. They'd rather believe in sorcery or astrology. Or as someone a hell of a lot smarter than me put it:

"“I worry that, especially as the Millennium edges nearer, pseudoscience and superstition will seem year by year more tempting, the siren song of unreason more sonorous and attractive. Where have we heard it before? Whenever our ethnic or national prejudices are aroused, in times of scarcity, during challenges to national self-esteem or nerve, when we agonize about our diminished cosmic place and purpose, or when fanaticism is bubbling up around us - then, habits of thought familiar from ages past reach for the controls.

It seems people have learned nothing from thousands of years of coastal regions being ravaged by storms and tsunamis.

Actually we have learned quite a bit. For example, we've learned how to let seaside property owners push their risk and losses off on other people who live hundreds of miles from the sea and don't even realize they're helping to pay for the recklessness of wealthy seaside property owners. http://www.fema.gov/national-flood-insurance-program

It seems people have learned nothing from thousands of years of coastal regions being ravaged by storms and tsunamis.

Actually we have learned quite a bit. For example, we've learned how to let seaside property owners push their risk and losses off on other people who live hundreds of miles from the sea and don't even realize they're helping to pay for the recklessness of wealthy seaside property owners. http://www.fema.gov/national-flood-insurance-program

It seems people have learned nothing from thousands of years of coastal regions being ravaged by storms and tsunamis.

Actually we have learned quite a bit. For example, we've learned how to let seaside property owners push their risk and losses off on other people who live hundreds of miles from the sea and don't even realize they're helping to pay for the recklessness of wealthy seaside property owners. http://www.fema.gov/national-flood-insurance-program

Mississippi floods.

As if the Mississippi hasn't naturally flooded regularly for the past zig-ten-thousand years...

"In the reconstructed analysis, there is no evidence of an acceleration in the long term rate of sea level rise, which remains at below 2mm/year. Furthermore an analysis of Southern Hemisphere sites suggests a slowing down in the rate. The sample sizes in both cases are small and give limited geographical coverage. Nevertheless, they give a similar coverage to the original Douglas study, which has generally been accepted as giving an accurate assessment of 20th Century rise. (For instance, the IPCC quote a figure of 1.7mm/year)."

2mm/year works out to 6.9 inches by 2100. Inches! Add another 7.8" for the next 100 years.

I see the Watts Signal has gone up over fair Gotham, calling all the lurkers back from under their bridges.